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Smartphones Ruin More Than Your Sleep — They May Also Be Destroying Your Vision

m01229/flickr Stop. If you are buying a new iPhone, don't use it in bed — and not just because nighttime smartphone use messes up your sleep cycle.

The blue light from personal electronic devices has also been linked to serious physical and mental health problems.

Blue light is part of the full light spectrum, which means we're exposed to it by the sun every day. However, nighttime exposure to that light, which is emitted at high levels by smartphones, tablets, laptops, and other LED screens, may be damaging your vision. It also suppresses production of the hormone melatonin, which throws off your body's natural sleep cues.

When your melatonin levels and sleep cycle go haywire, your risk goes up for a wide range of ailments, from depression to cancer.

Our various personal electronic devices emit blue light because it's so bright. That's the only way we can see those screens when the sun is shining. But we've started to have regular close-up nighttime exposure to this light only in the past 10 or 20 years, as a recent Gigaom story on the topic notes.

It should be noted however, that most studies show this effect with the light being held very close to the retina, which may not exactly replicate typical phone use.

2. There may also be a link between cataracts and blue light, though more research is needed. Gigaom cited an eye doctor who says he's starting to see 35-year-olds with eyes that are as cloudy with cataracts as 75-year-olds. Though a single account can't prove that blue light exposure causes cataracts — this doctor just thinks there's a link, which doesn't count as evidence — the idea is being investigated. Still, studies haven't concluded anything certain yet.

3. Exposure to blue light at night can ruin sleep. Bright blue light disrupts the brain's production of melatonin, a hormone that helps regulate the sleep cycle. That's fine in the morning, but our brains are supposed to start producing melatonin when we are ready for sleep, and blue light interferes with that process. That's why smartphones ruin sleep, and messing with your sleep has a long list of associated health consequences that range from obesity to genetic disruption and memory problems.

4. Sleep disturbance and "light at night" have been linked to higher cancer risk, particularly for breast and prostate cancers. In addition to helping us sleep, melatonin also functions as an antioxidant. And while more research is needed, researchers have pointed to "uninterrupted darkness" as potentially protective against cancer. People whose natural melatonin production is suppressed are at a higher risk for a variety of cancers, though a causal relationship has not been found.

5. Blue light may also take a toll on mental health. Research also shows that people whose melatonin levels are suppressed and whose body clocks are thrown off by light exposure are more prone to depression.

Our Weird Relationship With Blue Light

Despite the way this may sound, it doesn't mean that blue light is bad all the time. At times, it's actually beneficial to your health.

Light tells us when to wake and when to sleep. When bright blue light sends a signal to the brain to stop producing melatonin, it also primes your brain to start production of the hormone again later — in theory while you are getting ready for bed.

Experts say that getting an hour of sunlight in the morning helps people regulate their melatonin production and sleep cycle. They recommend getting some morning light without wearing sunglasses, so light gets through the retina and signals the pineal gland, which is what actually controls melatonin production.

That's great in the A.M., but when nighttime screen usage convinces our brains that it's morning and they shouldn't produce melatonin, that starts to wreak havoc on our bodies.